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Heart Anatomy
By: Collins Asadu‐Bempah
Heart
• PUMPS BLOOD
‐Oxygen
‐Carbon dioxide
‐Nutrients
‐Wastes
‐Electrolytes
‐Maintenance of PH and Homeostasis • Size of a fist
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Cone Shaped
Above diaphragm
Enclosed within mediastenum
300‐350g in males; 250‐300g in females… why?
Partially obscured by lungs
Apex ‐ PMI
• Covered in Pericardium ( peri =around; cardi =heart)
PERICARDIUM
• Double walled sac
2 Types
1) Fibrous Pericardium
Anchors heart to surrounding structures
Prevents overfilling of heart with blood
2) Serous (containing or secreting fluid) Pericardium
‐Parietal layer
Definition of PARIETAL. 1. a: of or relating to the walls of a part or cavity . b: of, relating to, or forming the upper posterior wall of the head; www.merriam‐
webster.com/dic onary/ parietal
‐Visceral layer
• Paricardial Cavity ‐ filled with serous fluid
‐fluid allows heart to move in friction‐free environment
*Pericarditis – inflammation of pericadium
‐roughens the surfaces of serous membranes impedes heart movement
‐ in severe cases, large amounts of inflammatory fluids will leak into the pericardial cavity and compress the heart and limit its ability to pump blood. Known as a Cardiac Temponade
3 LAYERS OF THE HEART
1) Epicardium – Superficial layer
‐ Visceral layer of serous pericardium
2) Myocardium – Middle, muscular layer
‐ Contractile layer of heart
*Myocarditis
3) Endocardium – Deeper layer
‐Thin white sheet of endothelium
‐lines heart chambers and valves
*Endocarditis
4 HEART CHAMBERS
2 Atria
2 Ventricles
*Interatrial Septum – a wall of tissue that divides the atria
*Interventricular Septum – divides the ventricles
• 2 main grooves/ landmarks indicating boundaries of the chambers ‐ Coronary Sulcus ( atrioventricular groove)
‐at junction of atria and ventricles
‐ contain the coronary arteries
‐ Anterior & posterior interventricular sulcus
ATRIA
*Crista terminalis – separates anterior & posterior regions of right atrium
*Fossa Ovalis – small depression located in right atrium. A remnant of the foramen ovale which is present during fetal development and allowed blood to flow from right atrium to left atrium
• Blood enters right atrium via 3 veins
• Superior vena cava
• Inferior vena cava
• Coronary sinus
VENTRICLES
Right Ventricle has larger anterior surface
Left Ventricle has larger posteroinferior surface
Left Ventricle is more muscular Trabecular Carneae ‐ irregular ridges of muscle lining the inner surfaces of ventricles
• Chordae Tendineae – strong, fibrous strings attached to the valves of the heart
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prolapse)
‐ prevent overexertion of the AV valve flaps ( i.e. prevents • Papillary Muscles – Anchor the chordae tendineae and keep them stretched
HEART VALVES
‐ Provide a unidirectional blood flow
‐ Made up of endocardium and connective tissue
‐ Attached to the chordae tendinae
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Tricuspid Valve
Mitrial (bicuspid ) Valve
Semilunar Valves
Aortic Valves
Right Atrium
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End point of systemic circuit
Right auricle
SVC
IVC
Crista terminalis
Fossa ovalis
S‐A node
A‐V node
Tricuspid valve
Right Ventricle
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Beginning point of pulmonary circuit
Trabeculae carneae
Papillary muscles
Chordae tendineae
Valve flaps
Pulmonary valve/semi‐lunar
Left Atrium
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End point of pulmonary circuit
Left auricle Pectinate Muscles Mitral valve
Left Ventricle
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Beginning point of systemic circuit
Thick wall
Trabeculae carneae
Papillary muscles
Chordae tendineae
Aortic valve
Vessels of Heart
A. Arteries
 Right coronary artery
 Nodal branch
 Right marginal a.
 Posterior descending a.
 Left coronary artery
 Circumflex a.
 Left marginal a.
B. Veins
 Coronary sinus
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Great cardiac vein
Middle cardiac vein
Small cardiac vein
Thebesian veins
Q&A
• Which Artery travels dorsal to the pulmonary trunk?
• Which is the only coronary vein that does not empty into the coronary sinus?
Cardiac Muscle
*Similar to skeletal muscle
‐ Striated
*Similar to Smooth muscle
‐ Gap junctions
Electrical System of the Heart
‐ Composed of “autorhythmic” or self‐excitable cells located at distinct regions of the myocardium
‐ 2 Types of Autorhythmic Cells
‐ Pacemaker Cells
‐ Conduction Fibers
• Sinoatrial Node (SA Node ) – located at right atrial wall
‐ the “pacemaker”
‐ ~70 impulses/ min
• Atrioventricular Node (AV Node) ‐ A variable resistor..WHY?
~50 impulses/min
• AV bundle
• Bundle Branches
• Purkinje Fibers
Figure 18.13 Pacemaker and action potentials of autorhythmic cells of the heart.
Threshold
Action
potential
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Pacemaker
potential
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1 Pacemaker potential
2 Depolarization The 3 Repolarization is due to This slow depolarization is due to both opening of Na+
channels and closing of K+
channels. Notice that the membrane potential is never a flat line.
action potential begins when the pacemaker potential reaches threshold. Depolarization is due to Ca2+
influx through Ca2+ channels.
Ca2+ channels inactivating and K+ channels opening. This allows K+ efflux, which brings the membrane potential back to its most negative voltage.
Copyright © 2010 Pearson Education, Inc.
HEART PHYSIOLOGY
CARDIAC CYCLE
*A 2 circuit system
‐Systemic ‐Pulmonary
*Deoxygenated blood enters the right atrium via the inferior and superior vena cava
‐Notice: AV valves are closed at this point because pressure in atria not great enough
* SA node fires and causes atria contraction ( P‐wave)
* AV valves open due to increased pressure in atria and blood enters ventricles
* There is a small delay before the electrical signal reaches the AV node; this allows enough time for ventricles to fill
*AV node depolarizes and ventricular contraction
*Ventricular Systole
‐ Isovolumetric contration
‐Ventricular Ejection
ISOVOLUMETRIC CONTRACTION
• All valves are closed
• Pressure in ventricles are great enough to cause AV valves to close but not great enough to cause SL and Aortic Valves to open
VENTRICULAR EJECTION
• Pressure is great enough to cause SL and Aortic valves to open and also to keep AV valves closed
• At this point the impulse has already reached the purkinje
fibers and QRS complex is evident
ISOVOLUMETRIC RELAXATION
• Ventricles repolarizes ( T‐wave) and cause the pressure to drop. The backflow of blood causes the SL and Aortic valves to close. • AV valves remain closed because the pressure in the ventricles is not low enough to allow valves to open
• Autonomic nervous system
• Sympathetic (accelerator) increases the HR
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Located in the medulla oblongata
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T1‐T5 spinal cord , pre/postganglionic fibers, •
Innervating the SA and AV node
• Parasympathetic (cardioinhibitory) sends impulse
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Dorsal vagus nucleus in medulla
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Lies in the ganglia in the heart wall •
Sends its fibers into the SA and AV node • Symp NS – releases NorEpi which binds to B1.
• Parysymp NS ‐ releases Acetylcholine which binds to Muscarinic cholinergic receptors and Gproteins. G proteins inhibit the opening of Calcium channels and also cause the opening of K+ channels which leads to hyperpolarization of the SA node
Cardiac Output
• The rate at which a ventricle pumps blood
( L/min)
CO= HR ( # contractions per min) X SV ( Volume of blood pumped from each ventricle per/ min
sources
• http://classes.midlandstech.edu/carterp/Cour
ses/bio211/chap18/chap18.html